1. Field of the Invention
The present invention relates to a liquid crystal display and more particularly to a liquid crystal display that is adapted to reduce the number of data lines and data drive integrated circuits corresponding to the data lines. The liquid crystal display of the present invention can be driven by a dot inversion system, using a data driver employing a column inversion method.
2. Description of the Related Art
A liquid crystal display controls the light transmittance of liquid crystal materials by using an electric field to display a picture. To this end, the liquid crystal display includes a liquid crystal display panel having a pixel matrix and a driving circuit for driving the liquid crystal display panel. The driving circuit drives the pixel matrix, so that picture information can be displayed on the display panel.
FIG. 1 illustrates a liquid crystal display, in accordance with the background art. In FIG. 1, the liquid crystal display includes a liquid crystal display panel 2. A data driver 4 drives data lines DL1 to DLm of the liquid crystal display panel 2. A gate driver 6 drives gate lines GL1 to GLn of the liquid crystal display panel.
The liquid crystal display panel 2 includes a thin film transistor (TFT) formed at each intersection of the gate lines GL1 to GLn and the data lines DL1 to DLm. The liquid crystal display panel 2 also includes liquid crystal cells connected to the thin film transistors and arranged in a matrix.
The gate driver 6 sequentially applies gate signals to the gate lines GL1 to GLn, in accordance with control signals from a timing controller (not shown). The data driver 4 converts data relating to the colors to be displayed, red (R), green (G) and blue (B), supplied from the timing controller, into video signals as analog signals. The data driver 4 applies the video signals for one horizontal line portion to the data lines DL1 to DLm, for every horizontal period as the gate signals are applied to the gate lines GL1 to GLn.
The thin film transistor (TFT) applies the data from the data lines DL1 to DLm to the liquid crystal cells in response to the gate signals from the gate lines GL1 to GLn. The liquid crystal cell is composed of a pixel electrode connected to the TFT and a common electrode, facing each other with liquid crystal therebetween. Thus, the arrangement is equivalent to a liquid crystal capacitor Clc. Such a liquid crystal cell includes a storage capacitor (not shown) connected to a previous gate line in order to sustain the data voltage charged in the liquid crystal capacitor Clc until the next data voltage is charged.
In this way, the liquid crystal cells of the liquid crystal display panel are located at intersections of the gate lines GL1 to GLn and the data lines DL1 to DLm, respectively. Thus, the number of vertical lines equals the number of data lines DL1 to DLm, i.e. there are m-number of vertical lines. In other words, the liquid crystal cells are arranged in a matrix to form m-number of vertical lines and n-number-of horizontal lines, corresponding to the number of the data lines DL1 to DLm and the gate lines GL1 to GLn, respectively.
As can be seen in FIG. 1, m-number of data lines DL1 to DLm are required to drive the liquid crystal cells formed into the m-number of horizontal lines. Accordingly, there is a disadvantage that a lot of processing time is spent because m-number of data lines (DL1 to DLm) are required to drive the liquid crystal display panel 2 of the background art. Moreover, there is a disadvantage that a lot of fabrication and design costs are required to manufacture the m-number of data lines (DL1 and Dlm) and the associated data driver integrated circuits (ICs) for driving the data lines DL1 to DLm.
In order to drive the liquid crystal cells on the liquid crystal display panel, the liquid crystal display device can employ an inversion driving method. Inversion driving methods include a frame inversion system, field inversion system, line (column) inversion system, and dot inversion system. In the frame inversion system, the polarity of the video signal applied to the liquid crystal cells on the liquid crystal display panel are inverted whenever the frame is changed.
In the line in-version system driving method of the liquid crystal display panel, the polarities of the video signals applied to the liquid crystal display panel are as shown in FIGS. 2A and 2B. The horizontal lines are inverted for each gate line of the liquid crystal display panel and for each frame. Such a line inversion system has a disadvantage in that flickers, such as stripe patterns, are generated between horizontal lines. The flickers occur because crosstalk exists between pixels in a horizontal direction.
In the column inversion system driving method of the liquid crystal display panel, the polarities of the video signals applied to the liquid crystal display panel are as shown in FIGS. 3A and 3B. The vertical or column lines are inverted for each data line of the liquid crystal display panel and for each frame. Such a column inversion system has a disadvantage in that flickers, such as stripe patterns, are again generated between vertical lines. Again, the flickers occur because crosstalk exists between pixels in a vertical direction.
In the dot inversion system driving method of the liquid crystal display panel, the polarities of the video signals applied to the liquid crystal display panel are as shown in FIGS. 4A and 4B. A video signal with its polarity contrary to those of the liquid crystal cells, which are adjacent thereto in a vertical and a horizontal direction, is applied to each liquid crystal cell. The polarities of the video signals are inverted for each frame.
In the dot inversion system, FIG. 4A illustrates when video signals of an odd-numbered frame are displayed. The video signals are supplied to the liquid crystal cells, respectively, for a positive (+) polarity and a negative (−) polarity to appear alternately as it progresses from top-left to right and down to the bottom in the liquid crystal cells. FIG. 4B illustrates when video signals of an even-numbered frame are displayed. The video signals are supplied to the liquid crystal cells, respectively, for the negative (−) polarity and the positive (+) polarity to appear alternately as it progresses from top-left to right and down to the bottom in the liquid crystal cells.
The dot inversion driving method causes the flickers, occurring among pixels adjacent in the vertical direction and adjacent in the horizontal direction, to offset each other. By this arrangement, pictures of better quality than the other inversion systems can be displayed.
However, in the dot inversion driving method, since the polarity of the video signal applied from the data driver to the data lines is inverted in a vertical and a horizontal direction, there is a disadvantage that the data driving method requires more power consumption than the other inversion systems. More power is required because of the amount of the change of a pixel voltage, that is, a high frequency of the video signal.